1. Field of the Invention
This invention relates to a cap for closure of the liquid opening of a container, and more particularly to a two-piece cap for a roller bottle.
2. Description of Related Art
One type of container commonly used in the laboratory for culturing of cells is known as a “roller bottle”. Roller bottles are generally cylindrically shaped and are adapted to rotate about their axes. The internal surfaces of such roller bottles are for providing active surfaces for cells. Following introduction of a liquid growth medium into the liquid opening of the roller bottle, the bottle is capped. The subsequent rotating movement of the bottle keeps the internal surfaces wetted with a liquid medium, thereby encouraging the growth of cells. Rotating rollers of an appropriate apparatus are employed to rotate these roller bottles.
Current caps used to seal the liquid opening of roller bottles, as well as flasks and centrifugal tubes are screw-on caps of a one-piece design. The mechanical advantage of a screw-type threaded cap is translated to an axial force, wedging the sealing mechanism into the inner rim of the container, forming a tight seal due to the interference fit between the sealing mechanism and the container rim. With the current caps, some of the torque required to seal and unseal the bottle is generated by the friction created when the sealing mechanism rubs against the container rim as it rotates with the cap during assembly and disassembly. The elimination or reduction of this friction translates to a lower torque required to attach and detach the cap from the container.
A problem associated with the one-piece design of the cap has been the large amount of torque required to remove the cap from bottles once the seal-area has become crusted with dried media. In particular, the roller bottle user must apply an especially high amount of torque to remove caps that are stuck to the bottle because the media contained within the bottle has dried between the cap and the bottle rim, acting as an adhesive. To remove a one-piece cap, the user must rotate the cap and grind the dried media against the sealing surface as the sealing surface rotates against the inner bottle rim.
A need exists, therefore, for an improved cap for roller bottles, flasks, centrifugal tubes and other containers where the ability of the user to attach and detach the cap using a low amount of torque is of importance. In particular, it would be advantageous to provide a cap with a sealing mechanism that was free to rotate about the axis of the cap, so that rather than rubbing against the inner rim of the bottle as the cap rotates, the sealing mechanism instead moves up or down as the cap moves up or down.